JP3733158B2 - White balance control method - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a white balance control method suitable for an image input apparatus that captures an image recorded on a photographic film with an image sensor and converts the image into a video signal.
[0002]
[Prior art]
As one form of video camera, an image taken on a photographic film or an image of a printed photograph is imaged by an image sensor such as a CCD solid-state image sensor or a MOS type solid-state image sensor, and appropriate photoelectric processing is performed on the obtained photoelectric signal There is known an image input device which performs video observation conforming to the NTSC system, and inputs it to a CRT monitor or video printer so that the image can be observed (for example, “FUJIX FOTOVISION FV7 commercialized by the present applicant”). ").
[0003]
In such an image input apparatus, since a photographic film is selected as a subject, even if white balance control as used in a normal video camera is performed, an appropriate color balance cannot always be obtained. For example, when trying to capture an image recorded on a color negative film,
(1) The film base itself is colored orange, and the degree of coloration varies greatly depending on the type of film.
(2) The color temperature of the light source that illuminates the film during imaging cannot be specified.
(3) The color temperature when taking a photo on the film is unknown.
For these reasons, when performing white balance control on these images, a special color temperature detection method and adjustment method are required.
[0004]
In view of these circumstances, the applicant has already filed an application regarding a white balance adjustment method suitable for the image input device. According to this, an excellent white balance adjustment is realized for an image recorded on a color negative film. be able to.
[0005]
[Problems to be solved by the invention]
However, the function of the image input device has been further improved so that not only color negative film images but also reversal film images and print photo images can be selected as general subjects as in ordinary video cameras. In this case, the adjustment methods proposed so far often cannot be dealt with. This is because, in order to achieve appropriate white balance adjustment while preventing color feria, it is necessary to narrow the detection range of the subject's color temperature to some extent. If the type changes, the color balance may be judged to be interrupted, and the white balance adjustment may be interrupted. Conversely, if the detection range of the color temperature is widened, the frequency of color failure will increase. Become. Such an adverse effect occurs not only when the color negative film is used but also when the type of the positive image is changed.
[0006]
An object of the present invention is to provide a white balance control method that eliminates the above-described drawbacks of the prior art and can perform optimum white balance adjustment for each type of subject selected as an imaging target. .
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention first selects a color integral value used for white balance control from each color integral value obtained by integrating a color signal for each area partitioning the imaging screen of the image sensor. Change the sorting criteria depending on whether the image being imaged is a positive image or a negative image And When the image to be imaged is a negative image, the largest maximum luminance integrated value is obtained from each luminance integrated value obtained by integrating the luminance signal for each area, and the maximum luminance integrated value is larger than a predetermined value. If it is larger, only the color integral value of the area where the maximum luminance integral value has been obtained is subject to sorting by the sorting criterion, and if the maximum luminance integral value is smaller than a predetermined value, the color signal is output for each area. Each color integrated value obtained by integration is set as a selection target according to the selection criterion. When the image to be imaged is a positive image, each color integration value obtained by integrating the color signal for each area is selected as a selection target based on the selection criterion. The color signal includes a red signal, a green signal, and a blue signal, and the selection criterion includes a ratio of an integral value of the red signal and an integral value of the green signal, an integral value of the blue signal, and an integral value of the green signal. It is determined in a range using the ratio of In addition, a convergence value of white balance control is set within the range that defines the selection criterion, and this convergence value differs between positive image capturing and negative image capturing.
[0008]
White balance control is completed when the combination of the detected red and green integrated values and the blue and green integrated values reaches the convergence value. This convergence value is used for positive images. , It is different for negative images. Furthermore, when white balance control is performed toward these convergence values, the amplification factors of the red signal and blue signal are increased or decreased by the control signal for each color, but the variable range depends on the positive image and the negative image. Can be switched. Also, reference preset data is set in each variable range, and when the white balance control is started, the amplification factors of the red signal and the blue signal are determined based on a control signal determined by the preset data.
[0009]
If the integrated luminance value obtained by integrating the luminance signal of all areas of the imaging screen fluctuates more than the predetermined change width, Even if the imaging target is not changed between the negative image and the positive image, the control signal at that time determined within the variable range is reset to the control signal corresponding to the preset data. As will be described later in the embodiments, white balance control is performed. For color integral value selection In addition to changing the reference and variable range of the control signal for white balance adjustment with a positive image or negative image, it can be changed for each type of subject, such as general subjects, print photos, positive films, and negative films. It is good to change to.
[0010]
【Example】
In FIG. 2 showing the external appearance of the image input apparatus using the present invention, a head portion 3 is provided on the upper portion of the main body portion 2. The head unit 3 includes a mount unit 4 in which a slit 4a is formed and a pair of illumination units 5 that are pivotally mounted on the mount unit 4 so as to be freely opened and closed. For example, when the developed photographic film 6 divided into sheets every six frames is held by the film holder 7 and the film holder 7 is inserted into the slit 4a and the illumination unit 5 is turned on, the illumination light is milky white film holder. The photographic film 6 is diffusely illuminated from the back side through 7.
[0011]
A pair of support legs 9, 9 are pivotally attached to the main body 2, and the main body 2 is supported in an upright state by opening it as shown in the figure. The main body 2 incorporates a zoom optical system and an image sensor known as, for example, a CCD or MOS type solid-state imaging device, and images an image recorded on the photographic film 6 as a still image. The photographic film 6 may be either a color negative film or a color positive film. Necessary signal processing such as negative / positive inversion is performed by appropriately operating the mode switching lever 10 according to the film type. The head portion 3 can be rotated 90 ° from the mount portion 4 with respect to the main body portion 2, and the image of the photographic film 6 is taken in the horizontal posture, even if it is taken in the horizontal posture. But it can handle it.
[0012]
Further, the support legs 9 and 9 can be rotated further upward from the illustrated position, and the illumination units 5 and 5 can be opened to support the main body 2 in an inverted state. In this state, for example, it is possible to illuminate a printed photograph placed underneath with the illumination units 5 and 5 and take an image thereof. Moreover, it can also be used like a normal video camera by opening the lighting units 5 and 5 and holding the main body 2 and directing it toward the subject.
[0013]
The main body unit 2 is provided with the following manual operation unit.
(1) Power switch 11
Operated when the power is turned ON / OFF. Further, it is also used as an ON / OFF switch of the inverter circuit 53 for turning on / off the lighting unit 5.
(2) Auto switch 12
When turned on, color adjustment (white balance, color density) and brightness adjustment are automated. When turned off, the color and brightness of the reproduced image can be adjusted by operating the volume dials 16 to 20.
(3) Mask switch 13
When an image is displayed on the CRT monitor depending on whether the image of the photographic film 6 is in the horizontal posture, the vertical posture, or the panorama size, when extra space around the image is electrically masked Operated. The mask range is switched depending on the number of times of pressing.
(4) Mode switch 15
Switching operation is performed when the imaging mode is changed. Imaging modes are as follows.
・ Camera mode
Mode for capturing images as a normal video camera.
・ Print photo mode
A mode in which the main body 2 is raised in an inverted state and a printed photograph (positive image) placed underneath is taken.
・ Positive film mode
A mode for capturing a positive film image set on the mount unit 4.
・ Negative film mode
A mode for capturing an image of a negative film set on the mount unit 4.
[0014]
(5) Manual volume dial 16-20
In addition to red and blue color adjustments, there are color density adjustments and brightness adjustments. These dials are effective when the auto switch 12 is turned off.
(6) AF switch 22
Used when switching between auto focus and manual focus, and as a start-up switch for setup AF.
(7) Manual focus switch 23
This is operated when focusing manually. With the + -two-way seesaw switch, the pressing operation is performed according to the focusing direction.
(8) Zoom switch 24
It is operated when zooming the zoom optical system, and is composed of a two-direction seesaw switch in the tele and wide directions.
[0015]
In FIG. 1 showing the functional blocks of the image input device, the zoom optical system 25 includes a focus lens 25a and a variable magnification lens 25b, and a front lens focus method in which the focus lens 25a is moved closer to the object side than the variable magnification lens 25b. It has become. Since the photographic film 6 is set at a short distance position of about 10 to 30 mm from the front end of the zoom optical system 25, the photographic film 6 is fixed to the object side of the focus lens 25a in order to cover the optical performance particularly with respect to obliquely incident light. A convex lens may be arranged. Also, various aberration correction fixed lenses may be provided on the image plane side of the variable magnification lens 25b.
[0016]
The focus lens 25a and the variable power lens 25b are moved by stepping motors 26a and 26b that are independently driven. The focus lens 25a and the zoom lens 25b move back and forth in the direction of the optical axis in the lens barrel 28 to perform zooming and focusing. Regarding the movement control of the focus lens 25a accompanying zooming, tracking data in which the position of the focus lens 25a is associated with the position of the zoom lens 25b is prepared in advance for several types of subject distances. When zooming is performed after focusing is completed, the position of the focus lens 25a can be determined based on the tracking data. For subject distances for which no tracking data is prepared, an interpolation calculation may be performed based on the prepared tracking data to calculate the position of the focus lens 25a.
[0017]
An image sensor 30 is fixed to the rear end of the lens barrel 28 so as to be positioned on the optical axis of the zoom optical system 25, and an optical image formed on the photocathode by the zoom optical system 25 is converted into a photoelectric signal. Output. The lens barrel 28 is incorporated in the main body 2 so that it can move in the direction of the optical axis as a whole. The lens barrel 28 is moved close to the photographic film 6 by about 10 mm by an external operation, and retracted by about 10 mm from the position. Any position can be selected. In the close position, the imaging range of the zoom optical system 25 is narrowed with respect to a photographic film at a certain position, and in the retracted position, the imaging range of the zoom optical system 25 can be widened. Therefore, the zoom optical system 25 is not scaled. In addition, it is possible to change the image magnification only by performing focusing at each position. In order to detect which position the lens barrel 28 is in, a tongue piece 28 a is provided on the lens barrel 28, and this is detected by a pair of microswitches 31.
[0018]
The photoelectric signal obtained from the image sensor 30 is adjusted to an appropriate output level by the gain control amplifier 33, converted to a digital signal by the AD converter 34, and input to the digital signal processing unit 35. The digital signal processing unit 35 performs various types of digital signal processing under the control of the CPU 36, and includes a signal processing circuit 35a, an integration circuit 35b, a synchronization signal generator 35c, an interface circuit 35d, and the like. The signal processing circuit 35a separates a photoelectric signal input as a digital signal into a luminance signal and a color signal, performs amplification for each color signal for white balance adjustment, and performs an appropriate signal such as matrix calculation or interpolation processing. Processing is performed to generate a video signal in the form of a digital signal. The video signal thus obtained is converted into an analog signal by the DA converter 37 and then output as a video signal in the form of a composite signal or RGB signal by the video amplifier 38.
[0019]
The integrating circuit 35b digitally integrates the color signal and the luminance signal obtained for each pixel from the signal processing circuit 35a. When the color signal is integrated, the red signal (R signal), the green signal (G signal), and the blue signal (B signal) are integrated. For this integration process, the imaging screen is divided into 64 areas as shown in FIG. ₁ ~ A ₆₄ Luminance integral value IY for each ₁ ~ IY ₆₄ , R signal integral value IR ₁ ~ IR ₆₄ , G signal integral value IG ₁ ~ IG ₆₄ , B signal integral value IB ₁ ~ IB ₆₄ Ask for. The integral data thus obtained is input to the CPU 36 via the interface circuit 35c.
[0020]
Further, the integrating circuit 35b has a function of integrating the change (absolute value) of the luminance signal for each adjacent pixel within a certain range including the entire imaging screen or the center of the imaging screen. Then, the sum total data for the luminance signal change is input to the CPU 36 as a focus signal. Since the change in luminance signal between pixels increases as the contrast of the image increases, the zoom optical system 25 is focused by adjusting the movement of the focus lens 25a while evaluating the level change of the focus signal by the CPU. be able to.
[0021]
The synchronization signal generator 35d inputs a synchronization signal to the CPU 36 and the sensor driver 40 that drives the image sensor 30, and operates them in synchronization. The synchronization signal is also supplied to each circuit unit in the digital signal processing unit 35, and the image sensor 30, the digital signal processing unit 35, and the CPU 36 are driven in synchronization with each other.
[0022]
The CPU 36 performs exposure control and focusing control in addition to performing white balance control, which will be described later, based on the integration data input from the digital signal processing circuit 35. The iris driver 41 is used to drive an iris motor 43 that opens and closes an iris (aperture) 42. The iris signal output from the CPU 36 is converted into an analog amount by the DA converter 44, and thereby the iris 42 is opened and closed. Since the level of the luminance signal obtained from the signal processing circuit 35a is changed by opening and closing the iris 42, the exposure control is automatically performed by adjusting the opening diameter of the iris 42 while monitoring the level change of the luminance signal by the CPU 36. It can be carried out.
[0023]
Further, if the output level of the photoelectric signal cannot be kept within an appropriate range by adjusting the iris 42 or the charge accumulation time of the image sensor 42, the gain of the gain control amplifier 33 can be adjusted to cope with this. it can. However, if the gain of the gain control amplifier 33 becomes too large, the S / N ratio of the photoelectric signal deteriorates. Therefore, it is preferable to determine the maximum gain value for each type of subject and adjust the gain within that range. . Furthermore, as the aperture diameter of the iris 42 increases, the optical performance (MTF) of the zoom optical system 25 deteriorates. Therefore, a limit aperture diameter is set in accordance with zooming, and is larger than this limit aperture diameter. Iris adjustment should be performed within a range that does not increase. The hall element 45 and the hall amplifier 46 are provided in consideration of this, and detects the rotational position of the iris motor 43 and inputs the aperture diameter information of the iris 42 to the CPU 36.
[0024]
The CPU 36 further supplies drive signals to the focus driver 48 and the zoom driver 49, respectively. Each driver 48, 49 supplies a number of drive pulses corresponding to the input drive signal to the stepping motors 26a, 26b, whereby the focus lens 25a and the variable power lens 25b move forward and backward in the optical axis direction. As described above, the CPU 36 moves and adjusts the focus lens 25a to the in-focus position while evaluating the focus signal input from the digital signal processing unit 35.
[0025]
The fluorescent fluorescent lamp 5 a incorporated in the illumination unit 5 is turned on by a power supply circuit 51, a DC / DC converter 52, and an inverter circuit 53. Then, the CPU 36 determines whether the self-illumination is turned on or off from the ON / OFF state of the inverter circuit 53. At the time of turning off, the electronic shutter time (charge accumulation time) of the image sensor 30 is 1/100 sec. When the lighting is confirmed by the signal, switching to 1/60 sec can prevent flicker noise from being superimposed on the video signal.
[0026]
Various operation signals described in the paragraphs [0014] and [0015] are input from the manual input unit 55 and the dial input unit 56, and the CPU 36 executes an imaging sequence based on these operation signals and performs various control operations. Switch the control mode. These sequence program and control program are written in the ROM area of the memory 58, and various flags and data obtained in the process of executing the imaging sequence are appropriately written and read in the RAM area. The EEPROM area stores data referred to in the execution process of the sequence program and the control program, such as tracking data used during focusing. Note that the memory 58 is actually integrated into the CPU 36.
[0027]
The EEPROM area of the memory 58 stores detection frame data and control range frame data that are referred to when white balance control is performed. The detection frame data is schematically represented as shown in FIG. In FIG. 4, the horizontal axis represents the ratio [IR / IG] of the G signal integral value IG and the R signal integral value IR, and the vertical axis represents the G signal integral value IG and the B signal integral value IB. The ratio [IB / IG] is taken. Three types of detection frames K1, K2, and K3 are set with these ratios [IR / IG] and [IB / IG] as parameters.
[0028]
These detection frames K1 to K3 are referred to when the CPU 36 determines whether to execute white balance control when the integrated values IR, IG, and IB of the respective color signals are read from the digital signal processing unit 35. Therefore, when the combination of the ratios [IR / IG] and [IB / IG] based on the read integrated value is within the respective frames, white balance control is executed. The detection frames K1 to K3 are properly used as follows depending on the imaging mode.
Detection frame K1: In camera mode
Detection frame K2: Print photo mode and positive film mode
Detection frame K3: in negative film mode
The detection frame data includes a convergence point O of white balance control for a positive image. _P And the convergence point O of white balance control for negative images _N It has been decided.
[0029]
The control range frame data is schematically represented as shown in FIG. In FIG. 5, the horizontal axis represents the control signal R of the R signal. _CONT , And the vertical axis represents the control signal B of the B signal _CONT There is. These control signals R _CONT , B _CONT Is input from the CPU 36 to the digital signal processing circuit 35, whereby the signal processing circuit 35a receives each control signal R. _CONT , B _CONT The R signal and the B signal are amplified correspondingly. However, four types of control range frames S1 to S4 are set corresponding to the imaging mode, and the control signal R _CONT , B _CONT It is forbidden for the combination of to protrude from the control range frames S1 to S4.
[0030]
The control range frames S1 to S4 are properly used as follows according to the imaging mode.
Control range frame S1: In camera mode
Control range frame S2: Print photo mode
Control range frame S3: In positive film mode
Control range frame S4: In negative film mode
In addition, preset data P1 to P4 serving as a reference for starting control are set at substantially the center of each control range frame S1 to S4.
[0031]
Next, the white balance control processing with the above configuration will be described with reference to the flowchart shown in FIG. First, the CPU 36 performs exposure control according to the set imaging mode, and adjusts the output level of the photoelectric signal input to the digital signal processing circuit 35 to an appropriate level. For this exposure control, center-weighted metering is performed when the imaging mode is the camera mode, and average metering is performed for the entire imaging screen when the imaging mode is any other mode. Then, the aperture diameter control of the iris 42 is performed so that each photometric value matches the target photometric value at which proper exposure is achieved. Even when average photometry is performed, if the average photometry value is significantly different from the center-weighted photometry value, the target photometry value is corrected by determining that the scene is a backlight scene or a spotlight illumination state.
[0032]
After the exposure control is performed in this way, it is confirmed that the color adjustment switch 12 is auto, and the white balance control process is started. When the white balance control is started, as shown in FIG. 6, it is first determined in step 1 (ST1) whether the imaging target is a negative image or a positive image. For this determination, the CPU 36 reads the set position of the mode switch 15 based on a signal from the manual input unit 55. The process branches to “Y” when the imaging mode is the negative film mode, and branches to “N” otherwise.
[0033]
When the negative image is identified as the imaging target, the CPU 36 operates the signal processing circuit 35a in the negative / positive inversion mode, converts the input photoelectric signal into a negative / positive inversion photoelectric signal, and converts the luminance signal. , Separate into each color signal. The integrating circuit 35b integrates the luminance signal and each color signal after conversion. The integrating circuit 35b firstly displays each area A obtained by dividing the imaging screen. ₁ ~ A ₆₄ Luminance integral value IY obtained for each ₁ ~ IY ₆₄ Is read. Then, as shown in ST2, area A ₁ ~ A ₆₄ The highest (brightest) maximum luminance integral value IY _m To extract.
[0034]
In ST3, the maximum luminance integrated value IY thus obtained is obtained. _m Is compared with a predetermined set value α, and the processing branches depending on the magnitude. And "IY _m If ≧ α, split screen integral type white balance control is performed, and “IY _m If it is <α, addition screen integration type white balance control is performed. The set value α is the maximum luminance integrated value IY. _m Is determined to be the luminance value of the white portion in the imaging screen, and is set to a value slightly larger than the luminance integrated value IY obtained from each area when the subject is uniform white, for example. .
[0035]
In the split screen integral type white balance control, the maximum luminance integral value IY _m The white balance is adjusted so that the area is reproduced as white. That is, the maximum luminance integral value IY _m Area A where is obtained _m , Integral value IR of each color signal of R, G, B _m , IG _m , IB _m A control signal R that determines the amplification factor of the R signal and the B signal so that a white color is obtained by summing _CONT , B _CONT The value of is controlled.
[0036]
On the other hand, in the addition screen integration type white balance control, white balance is adjusted based on the knowledge that when the respective color signals of the entire imaging screen are averaged, the color becomes gray (achromatic color). For this reason, each area A of the imaging screen ₁ ~ A ₆₄ Integrated value IR of the color signal obtained from ₁ ~ IR ₆₄ Sum total integral value ΣIR, integral value IG ₁ ~ IG ₆₄ Sum total integral value ΣIG, integral value IB ₁ ~ IB ₆₄ Is calculated so as to be white when the sum is summed. _CONT , B _CONT The value of is controlled. As will be described in detail later, each area A ₁ ~ A ₆₄ When obtaining the total integrated values ΣIR, ΣIG, and ΣIB, a process of excluding extremely separated colors from the addition target is performed.
[0037]
In ST4, it is determined whether white balance adjustment is possible. For this reason, the CPU 36 uses one of the detection frames K1 to K3 corresponding to the imaging mode. For example, the detection frame K3 is used when the negative film mode is set, and the maximum luminance integral value IY is used during the white balance control of the split screen integral type. _m Area A where is obtained _m Integral value of IR _m , IG _m , IB _m These ratios [IR _m / IG _m ], [IB _m / IG _m ] Is calculated. When the detection point is not included in the detection frame K3 by these combinations, the process shifts to the data exclusion process and the white balance control is stopped. Because this is the area A _m This means that the color is extremely red or blue, or the color tone is very dark or light. In such a case, if the white balance adjustment is forcibly performed for the color of this area, the possibility of color failure becomes extremely high.
[0038]
On the other hand, at the time of addition screen integration type white balance control, the detection point determined by the ratio [IR / IG], [IB / IG] for each area is compared with the detection frame K3, and the detection point is outside the detection frame K3. The data is excluded and the data of the area included in the detection frame K3 is selected. This data selection can prevent the white balance from being affected by the biased color in the imaging screen even when the addition screen integration type white balance control is performed. For the integrated values IR, IG, IB for each area thus selected, the total integrated values ΣIR, ΣIG, ΣIB are calculated, and the ratios [ΣIR / ΣIG], [ΣIB / ΣIG] are obtained.
[0039]
In the process of ST5, the ratio [IR _m / IG _m ], [IB _m / IG _m ] Or a detection point determined by the ratio [ΣIR / ΣIG], [ΣIB / ΣIG] is a convergence point O shown in FIG. _N , O _P Compared with In the negative film mode, the detection point is the convergence point O. _N Control signal R in the direction approaching _CONT , B _CONT Increase or decrease. Control signal R _CONT , B _CONT When increasing / decreasing, one of the control range frames S1 to S4 is selected corresponding to the imaging mode.
[0040]
When the split screen integral type white balance control is performed in the negative film mode, the control range frame S4 is selected, and first, the control signal R determined by the preset data P4 is selected. _CONT , B _CONT As a result, the R signal and the B signal are amplified. As a result, area A _m Integrated value IR obtained from _m , IG _m , IB _m And ratio [IR _m / IG _m ], [IB _m / IG _m ] Changes. The CPU 36 again performs the ratio [IR by the process after ST4. _m / IG _m ], [IB _m / IG _m ] Is determined by the convergence point O _N Control signal R until _CONT , B _CONT The same processing is repeated while increasing or decreasing the value of.
[0041]
Control signal R _CONT , B _CONT When increasing or decreasing the control signal R _CONT , B _CONT In ST6, it is determined whether or not the control point determined by the combination of these is out of the control range frame S4. When the control point deviates from the control range frame S4, the white balance adjustment is stopped at that point. Further, the control signal R within the control range frame S4. _CONT , B _CONT While performing processing while increasing / decreasing the detection point and the convergence point O according to the determination of ST7 _N Is detected, the white balance adjustment is completed at that time, and the signal processing circuit 35a controls the control signal R determined by the previous processing. _CONT , B _CONT As a result, the R signal and the B signal are amplified, and good white balance adjustment is performed.
[0042]
Detection point is convergence point O _N When the white balance adjustment of the split screen integration type or the addition screen integration type is performed, the ratios of the color integration values IR, IG, and IB of the area to be evaluated for color adjustment are averaged. This means that a good white balance image was obtained. Also, if the control point deviates from the control range frame S4 in the middle of the above, it means that there is a high possibility that color failure will occur when the white balance adjustment is forced, so the white balance adjustment is stopped at that point. By doing so, it is possible to perform white balance adjustment within a range that does not result in color failure.
[0043]
In this way, in the negative film mode, the split screen integration type white balance control and the addition screen integration type white balance control are properly used according to the luminance signal distribution in the imaging screen. White balance can be adjusted.
[0044]
When the imaging mode is the camera mode, the print photo mode, or the positive film mode, the addition screen integration type white balance control is performed. The control frames K1 and K2 and the control range frame S1 correspond to each mode. The control signal R is exactly the same except that ~ S3 is properly used. _CONT , B _CONT Increase / decrease is performed. Even when performing addition screen integration type white balance control, inappropriate data exclusion is performed by the processing of ST4, so even if the scene is changed, appropriate white balance adjustment is realized. Is done.
[0045]
Incidentally, a plurality of types of detection frames K1 to K3 and control range frames S1 to S4 are prepared in accordance with the imaging mode, and these are selected and used as appropriate, for the following reason. In the case of the negative film mode, there is considerable variation in the color of the film base to be imaged, and the color temperature of the illumination light source at the time of photography is also assumed variously, so the detection frame K3 is set to be wide. The control signal R is also applied to the control range frame S4. _CONT , B _CONT It is better to give some degree of freedom to the range of increase and decrease.
[0046]
In the print photo mode and the positive film mode, the detection frame K2 is set narrower in that the color of the image taken on the print photo and the positive film matches the color of the reproduced image. Further, the control range frame S2 in the print photograph mode is set so narrow that the color reproducibility of the print photograph itself does not change so much. The control range frame S3 in the positive film mode is slightly wider so that it can be used even when a commercially available light box or slide viewer is used in addition to the built-in fluorescent lamp 5a as an illumination light source. Is set.
[0047]
On the other hand, in the camera mode, the white balance must be adjusted with respect to the color temperature of various illumination light sources, so the detection frame K1 is set wide. The pattern of the control range frame S1 is determined so as to correspond to the color temperature of various illumination light sources.
[0048]
In this way, white balance control is performed corresponding to each imaging mode, and when the images are sequentially changed in the imaging mode, the set control signal R _CONT , B _CONT Does not fluctuate significantly. However, large exposure fluctuations, that is, each area A ₁ ~ A ₆₄ Luminance integral value IY of ₁ ~ IY ₆₄ When the sum of the values changes more than a preset change width, the detection point may protrude from the detection frame set at that time. Therefore, in such a case, the control signal R set at that time is set. _CONT , B _CONT Is returned to the value of the preset data P determined within the control range frame, and white balance control is performed again under the imaging mode. In addition, when there is a change in the imaging mode, the control signal R set at that time is also used. _CONT , B _CONT Is cleared, the detection frame K and the control range frame S corresponding to the changed imaging mode are selected, and the control signal R _CONT , B _CONT To the value of preset data P corresponding to the imaging mode.
[0049]
Further, when a photographic film is an imaging target, the head unit 3 may be rotated according to the length and width of the photographic image. When such an operation is performed, an adjacent photographic image may enter the imaging screen, or the photographic image may be electrically covered with a black mask or a white mask by the operation of the mask switch 13. When such an operation is performed, a large change occurs in the exposure fluctuation and the integrated value of each color signal, and the white balance control greatly fluctuates. In order to avoid this, when a rotation operation or mask switch operation of the head unit 3 is performed, the control signal R obtained by the white balance control so far is performed. _CONT , B _CONT Is saved as is. The mask when the mask switch 13 is operated is preferably switched to a black mask when displaying an image on a CRT monitor, and to a white mask when outputting a video signal to a video printer for printing.
[0050]
Further, in the embodiments so far, the white balance control detection frame and the control range frame are switched in the camera mode, the print photo mode, the positive film mode, and the negative film mode, respectively. Basically, the detection frame and the control range frame may be switched depending on whether the subject is a positive image or a negative image.
[0051]
【The invention's effect】
As described above, in the white balance control method of the present invention, white balance control is performed depending on whether the image to be imaged is a positive image or a negative image. For color integral value selection Since the standard has been changed, white balance control is performed with a standard suitable for each image. Of color integral value used for Whether or not it is possible can be determined, and color balance can be prevented and good white balance control can be performed.
[0052]
White balance control The color integral value used for Are determined for the positive image and the negative image in advance based on the combination of the ratio of the red signal integration value and the green signal integration value obtained from the photoelectric signal and the ratio of the blue signal integration value and the green signal integration value. The detection frame includes a combination of the ratio of the red signal integration value and green signal integration value obtained from the photoelectric signal when the frame is set and actually captured, and the ratio of the blue signal integration value and the green signal integration value. The detection frame set appropriately according to the positive image and the negative image can be used. Ho Since the convergence value of the light balance control can be set individually, white balance control with high versatility is possible.
[0053]
Furthermore, when white balance control is performed, the amplification factors of the red signal and blue signal are increased or decreased by the control signal for each color, but by changing the variable range according to the positive image or negative image, the white balance is controlled. It is possible to prevent color feria from occurring during the control. Also, by setting preset reference data in each variable range, and determining the amplification factor of the red signal and blue signal at the start of white balance control or when a large luminance change occurs based on this preset data The white balance control can be performed efficiently and in a short time following the change of the scene.
[Brief description of the drawings]
FIG. 1 is a functional block diagram of an image input apparatus using the present invention.
FIG. 2 is an external view of an image input apparatus using the present invention.
FIG. 3 is an explanatory diagram of area division of an imaging screen.
FIG. 4 is an explanatory diagram of a detection frame used for white balance control.
FIG. 5 is an explanatory diagram of a control range frame used for white balance control.
FIG. 6 is a flowchart showing a flow of white balance control processing.
[Explanation of symbols]
6 Photo film
25 Zoom optical system
30 Image sensor
33 Gain control amplifier
35 Digital signal processing unit
35a Signal processing circuit
35b integration circuit
36 CPU
58 memory

Claims (7)

In a white balance control method used for an image input device that captures an image of a photographic film or a printed photograph with an image sensor, converts the image into a video signal, and outputs the video signal.
The image to be imaged is used as a selection criterion for selecting a color integral value used for white balance control from each color integral value obtained by integrating the color signal for each area that divides the imaging screen of the image sensor. Change depending on whether the image is positive or negative ,
When the image to be imaged is a negative image, the largest maximum luminance integrated value is obtained from each luminance integrated value obtained by integrating the luminance signal for each area, and the maximum luminance integrated value is larger than a predetermined value. If it is larger, only the color integral value of the area where the maximum luminance integral value has been obtained is subject to sorting by the sorting criterion, and if the maximum luminance integral value is smaller than a predetermined value, the color signal is output for each area. A white balance control method characterized in that each color integration value obtained by integration is a target of selection based on the selection criterion . When the image that is imaged is a positive image, according to claim 1, characterized in that the interest of the sorting by said sorting based on the respective color integral value obtained by integrating the color signals for each area White balance control method. The color signal includes a red signal, a green signal, and a blue signal, and the selection criterion includes a ratio of an integration value of the red signal and an integration value of the green signal, and a ratio of an integration value of the blue signal and the integration value of the green signal. 3. The white balance control method according to claim 1, wherein the white balance control method is defined within a range in which the parameters are set as parameters. 4. The white balance control according to claim 3 , wherein a convergence value of white balance control is set within the range defining the selection criterion, and the convergence value is different between positive image capturing and negative image capturing. Method. 2. A variable range of a control signal that determines each amplification factor of a red signal and a blue signal for white balance control is changed according to whether the imaging target is a positive image or a negative image. 5. A white balance control method according to any one of 4 to 4 . Sets preset data within the variable range of the respective claim 5, wherein at the start of the white balance control, characterized in that to determine the respective amplification factors of the red signal and blue signal by a control signal corresponding to these preset data White balance control method. When the integrated luminance value obtained by integrating the luminance signals of all areas of the imaging screen fluctuates more than a predetermined change width, the amplification factors of the red signal and the blue signal are reproduced by the control signal corresponding to the preset data. The white balance control method according to claim 6 , wherein the white balance control method is set.

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